Consumers shopping for books at Barnes and Noble often use their phones or tablets to do a bit of comparison shopping by calling up Amazon’s website. There is no telling how much business Amazon has generated this way. Ironically, Amazon has recently received a patent for an algorithm making it harder for shoppers to check out competitors’ pricing online while at an Amazon owned retail store.

The patent makes it more difficult for a shopper hooked up to the store’s Wi-Fi network to visit the website belonging to an Amazon competitor. The Physical Store Online Shopping Control patent analyzes the websites being visited by a particular shopper. If the algorithm determines that the website belonging to a competitor is going to be accessed, it redirects the customer to Amazon’s own site, or to other sites approved by Amazon. The customer might even receive an Amazon coupon on his phone, or get approached by an Amazon sales rep trying to persuade the customer to make his purchase right on the spot.

Amazon now owns six physical bookstores, and will soon own 465 Whole Foods markets. Amazon’s patent will prevent customers inside these stores from doing any comparison shopping that might save them money, but at the expense of Amazon’s profits. Funny what happens when the shoe is on the other foot.